1. Field of the Invention
The present invention relates to chamber door closures and, more particularly, to guide mechanisms for chamber door closures.
2. Description of the Prior Art
There exists a wide variety of apparatus for effecting the closure of chamber doors. For example, a sterilizer chamber that operates under pressure must have a closure which effectively seals the chamber against fluid flow. Makhijani, U.S. Pat. No. 4,352,439 which issued on Oct. 5, 1982, describes an apparatus for closing the door of a pressure chamber. The apparatus includes an operator for moving the chamber door among its closed position, its partially closed position and its open position. The apparatus also includes a movable cam member which is capable of being forced by the operator between the door and a stationary flange positioned near the chamber opening to move the door into its closed position. The Makhijani apparatus includes a guide disposed on the chamber for restricting the movement of the door to that necessary for it to travel among its three positions. The guide is a flanged member on each side of the front of the chamber. In the embodiment shown, the door slides vertically along the flanged members between its partially closed and open positions. The door moves horizontally within the limits of the flanged members between its partially closed and closed positions. In the closed position the door is held securely to the chamber by the movable cam member wedged between the door and the stationary flanged member. In the partially closed and open positions, however, the door is free to move within the horizontal limits of the flanged members, thus, permitting some play in the door as it is moved vertically between the partially closed and open positions. In these positions, the door is not secured to the chamber sufficiently to prevent such play.
In a quick closing door for a pressure chamber, like that described by the Makhijani patent, there is a need to protect the seal from unnecessary wear. Repeated rubbing against the seal which can occur due to play in the door as it is opened and closed can prematurely wear the seal. In addition, the play in the door wears against the flange members and the outer edges of the door and places uneven stress on the cable system supporting the door during movement. Further stress is placed on the cable system when the door is rotated away from the chamber to replace the seal or service the sterilizer because the weight of the door is not supported by the chamber. The play in the door as it moves between the partially closed and the open positions can hamper the ease of movement and be noisy.
There is a need, therefore, for a guide mechanism for use with an apparatus to open and close the door of a chamber. There is a further need for such a guide mechanism which will maintain the door in alignment with the chamber to prevent wear of the seal and the door and to eliminate uneven stress on a cable system holding the door.
There is a need for a mechanism which permits the door to be moved away from the chamber for servicing the seal, the chamber or the door without placing undue stress on the closure system. Finally, there is a need for a mechanism which secures the door to the chamber when the door is being opened and which permits the door to expand and contract independently of the mechanism in response to the heat and pressure changes within the chamber when the door is closed.